Synchronizing system for telegraphy



- either of the signalling tone frequencies.

2,483,786 s l i over a wire line without-the aid of 'a carrier wave., Relay 8 is controlledby any conventional code.

keying device, such as a tape transmitter. One

or several such transmitters may be emp1oyed depending upon Whether the signals are to be transmitted over a simplex channel or whether time division multiplex channels are provided."

As shown in Fig. 1 a rotary distributor I0 comprises a segmented ring having eighteen segments II and a solid collector ring I2. The individual segments II are connected respectively to keying Other code element keying v furthermore for the transmission of code signals,

having ve or more code elements. 'I he essence of my invention is, therefore, independent of the design of the distributor.V v Infact, it is contemplated that in certain applications a rotary dis-` tributor would'be vdispensed with and an elec-- tronic distributor would be substituted. Y Y The utilization circuit on the output side of the frequency source I has a second branch indicated; by the conductor |20 which leads to afrequency divider I4 and thence to-a wave shaper I5. In. certain instances the frequency divider I4 may be, dispensed with and the wave shaper I5 may have its input circuit coupled to the output side of thel frequency divider 2. The question of whether. the frequency divider 2 may or may not be sufcient is determined by the ratio tobe chosen between the signalling tone frequencies and thev frequency of an alternating current to be usedy for energizing a synchronous motor II which drives the distributor I8. Preferably, however, the synchronizing frequency will be lower than It -is to. be understood, therefore, that the frequency divider units 2;, andvlll` may besuch as to develop output frequencies suitable for their respective utilization requirements. The frequency division may also be obtained in one or a pluralityof stages accordingfto the convenience anddesign economy of electronic devices within Lthe divider units.

The purpose of the wave shapers 3 and I5 is to improve the sign wave characteristics of the ,output from the respective frequency dividers 2 and Id and to suppress unwanted harmonics as far as possible. The wave Shaper 3, however, must pass two harmonics of the output from the frequency divider 2 and is, therefore, so designed as to favor the particular harmonics which are chosen to represent the mark and' space frequencies. :In the case of the wave shaper I5 a single frequency of output is desired and this frequency 'is one which is selected for amplification in any ampli-i fierunitlt from which'energy is obtained to drive the synchronous motor Il This motor` is connected to the shaft of'the distributor on which a brush arm I8'is mounted. The-brush arm,

carries brushes I3 which wipe over the segments I i and the solid ring I2 so as to successively co1- lect the signal pulses of positive and negative polarity and to apply the same for purposes of controlling the operation of the polar relay 8.

From the foregoing description of Fig. 1 it will be seengthata` constantfrequency` relationship is A.maintained between the rate of transmission of the code signals and the frequencies of the v'marking and spacing tones which are used to charaterizethe code signals.

In the description ofFig. 2 to follow it will also be observed that the frequencies of the marking and spacing code elements are themselves capable of utilization for VIVpurposes' of synchronizing the receiving distributor with the synchronous speed of the transmitting`` distributor.

Referring now to Fig. 2 I show therein a filter 2U the purpose of which is to improve the signalto-noise ratio and pass the two-tone audio signals which maybe derived from 4any conventional receivingunit. The output from theriilter 20 is fed toranampliiier and limiter unit 2I which in turn ,delivers an Aoutput across acoupling capacitor 22 to a. branched circuit in the respective arms of whichV are three resistors 23, 24 and 25.

The branches containing-resistors 23 and 24 will rstbe described as portions of the apparatus for translation ofthe code-signals. l A'twin diode dischargetube 26 has its electrodes suitably connected to inputand outputcircuits so that pulses of one polarityare derived from the marking frequency,l and pulses of .oppositelpolarity; are,.derived from `the ,spacing frequency. Thusone cathode 21 and one .anode 30are connected to the input circuit whilethe other cathode-29 and-the otherv anode 28 are connected to the outputcircuit.; Atank circuit fs is adjusted toresonate, ,with the spacing tone frequency. Another tank circuit fm is adjusted to resonate withthe the marking tone frequency. One terminalof 'each tank circuit is grounded The marking, tone frequency jm upon being rectified across the space path between cathode 21 and anode28 traverses anmoutpllt :circuit resistor 3=I andthus biases to cut-01T a grid 35, in tube` 3,2

of .azfconventional lockingfcircuit, `Iube32 and tube 33 are so associated inthis locking circuit as,-.to. produce azrectangular wave lthe peaks of which Irepresent marking elementsiand the vvalleys of which :represent spacing code elements@ The rectification ofthe spacing frequency fs takes place across the rectifier electrodes 29 and 3B in the twin vdiode tube 2t.v `The vpolarity of these rectified pulses is such that when they traverse=.the;resistor3l. the Ygrid 3,6 in the locking,

circuit. tube 3.2 is positivelybiased and renders thistube conductive. Y .I

Capacitors 34 areconnected respectively to the two branches of -theoutput circuit from tube 26 and are used for grounding the ripplecomponent of the tonenfrequencies, thus smoothing out the pulsesas delivered .to the controlA lgrid 36 of tube 32. Capacitor 35 is connected between this grid and ground and serves further for smoothing purposes. u

The details of tubes `32: and 33 are Ywell, known and -need not, therefore, bewfurther described herein. The output mayfbe takenoff ,of either one of thev anodes in the tubes 32 and 33, but it is here shown that this output lis conducted through a resistor 3lV to the control grid in anamplier tube 38. The connections for tube 38l are also conventional and while'this tube is shown as a pentode, other types ther locking circuit comprising of :amplifier itunes veiner, l:.o `--course, ne.. chosen. The :anodeA circuit :for :tune 313` be :traced noinmi.'v source-15H13.. C. ranode potentialcthe posi.- tiV-.e-.ctermnal eB .fof l which :.is. connected to 1 a ccmmonfcondueteri A-leadingatoas many selector' magnets asmay. be 'required one-.ora plurality ofiprinters orothei: zcddetranslatingieuices. The individuaieci-rcuits '.orethe :printeraselector mag-.- nets :.areshown-:connected' respectively@ dit-:rent segmentsxfAL-of;larotarydistributor. s inthe-.aspe-r cic embodiment herein illustrated these-rsegments are .eighteen .in lnumber and may-be grouped -as `forrechannelvniultinlex reception. The .respective .groups :are 'labeled v.el'h-annelt,` Channei; if and "Ghannel HI; `eac-h. 'havingsixicon ductors which represent fthe unitsofxafmt code. .-Apcollectorringll is connected=-to-fthe anodeifim tuber. The: distributor :brush iis.r com pletesithe. anode circuit-'through tubelfand successive'ly through theprinter magnets,v ther latter beingiselectedi iorenergization Iwhenever tube 3Bv is rendered conductive. vA. voltage-.divider1comprisingresistor sectionsi TH ,.1252 and l13l'is connected acrosstheiterminalsnot tha-Dfsource, the negative :terminal bei-ng ;S-grounded.Y VTherecreo-r1w grid ofatubef 36. isfconnected to the ljunction between resistors l'l and The'fcathode is connected to the junction betweenresistorsi .and i3.' 'The ohmic values offthese resistors-"i1, 'i2 i and `f7l-3 are such :that tube Sais normally non-conductingbut may. be rendered conductive byv 1a i positive pulse-applied tofitslgrid through resistori". 'Froml-the. foregoing: description -oi` the receiving circuiti it-vJill-be observed thatthe incomingsig` nal :elementsi are distinguished byv their frequencies 'imma-nd l22.-representing..'markingA and spacing units respectively. 'The Y signals are, therefore,l subjectedto: rectification in the-twin diode rectiL- ieivftube 25, the out-pui? from Wlzlich-V isfutilizedfin controlling the locking! `circuit in which ytubes 1321 andro@ are.- disposed. V VThe vsignals are then de-v livered' byrtherl'ociring circuit tothe amplifier-tube 38; 'the output froirpwhichA is fedi/through 'the distributor? to the. selector magnets nfsuccession.- Themagnets areselectively-actuated onlywhen tube 3=8 isrenderedconductive; e

I shall now describe thex'portion ofFgJZWli-'ich relates to synchronizing controlet 'the` receiving distnibutor M v ''It. lwas previously stated'L that* the output from theY amplifier-and limiter unit '2l is ltobefed1 across coupling ycapacitor ft2 tofthreebranches, of which the branches containing-resistorslilflanrif 24f2a-re-related'-' to Athe-code signal translator: `-The branch containing vresistor '-25f-s u sed--solely 'for pisuposesfY oft synchronizing-the distributorld'.

The tone signal: potentials owing through resisters 25=andl 52'fto groundy are utilized in the controlf.- offatwin. tr-io'de limiting famplier :tube 45'. The. purpose of. thistube is: to exercise-syn. chronizing control overf the. operationiof` a multi-. Vibrator 4.tube ci 5; which is also .ofv` the twin triode type. The circuit components of thesentubes andf'lE-.zwll rst- .be descrihed .aiteriwhichitheir Operation in azpleferred; embodiment .willebe fset forth snecincally by'waycfg-example.

.51.1.1 tubefll-aspacepathzayis defined-by anal-.hel 0de 46 and aneanodeffSy-af control gridr'rbeing, interposed. Likewise;l the spacepathb; is; defined byte. cathodes andan; anode-51;, a controllgrid ll.` beine interposed. Resistor 52. interconnects; the.Y control; varid 41. and :ground ,Resistor .5.4i intercom-.lents1 the cathode 46 and. ground. ca pacitor 551s in shuntgwith resist-.01154;

' output frequency-"from tube and thescathodeilsp 'cathode 1 is directly grounded. I ,-'Anode potential; :iromlthe .lfsource indieatedcasl-FB is :fedithroughA resistor E6 to anode Mirafncl:tluougfl'r resistor 'iiftoftheanode 5t. :Control grid:iisl.coupledtothemnodef throughacapacitori. 1

multivibrator tube ST5 possesses rtwosspace paths/c ianded, .space :pathm c being dened :by cathodefland anode 73,1 between:ii/leienacon-V trol sgrid'fysis; interposed. 'The spacel path` dlis definedfby-mcathodet9 Sand anode 1, between which acontrolhgrid 'isrinterposed AThe-con trolegrid 111 is connected to the grounded cathode fifthrough fav resistor 162. The YControl grid 80 iswconnecte'dto ylgrocmd thretugh-fa`v resistor V8111.' The cathode 19 is also connected to ground through al potenti'ometerr 63 in serieswithalresistor .G3 3': i l potential is'` suppliedl from` the source.;terminalPto-anodei `tl'iroughl a poten# tfiometer aand. to anod'elirthrough ya. resistor *Betweenthe `anode T8 off space path-'c andthe control-'grid 18o-'1 off space -npath --cZ--al crossv coupling capacitor is connected. Between theanodellil of space path d and the control grid TI of space path c a cross coupling vrcapacitor 8S is connected.

Itis Well -known that the circuit constantsV of.

ay multivibrator lmay begsoir a'djustedthatpit lwill` act'as'arequen'cy divider underV controlfoftrainsf oi impulses used to build up a certain charge on. a time constant circuit; "ifhertriggeringrlaction -ma-y; thus-be mad'esfuc'lgfthjat the rectangular Wave output 4will be a certain sub-harmoniciof` the input frequency.l `Irryth'e arrangement of my invention, howevergit is desired'-that the` out'-v p'ut x-i'requenc-zy bemaintaine'd constant while it isf-locked in step with either oneof theI higher tonerfrequenciesiused @as mark 'and SDac'e signal components'. I', therefore.,V provide vtwo 4time constant', circuits `Vfor transferring control 'froml tube- Mirto-tube '151 One ofthesetime 'constante circuits comprises a capacitor Eiland a portion o'fthe potentiometer llgjzthese l,elements being connectedbetweentheano'des 48 and 18 in the two tubes' respectively. The other time constant circuit isiconnectedbetween the anode 45l in the. tube 45and^the cathode 19in tube 15 and includes capacitor-"Grin [series with aportion vof `the potenucmeterss. i

'iNowfI-shall 'describe"thepperationgof tubes 45v andf'lf. Theirpurpose' is to"full1 the requirements-of a synchronizing system. The` rectangulanwavejoutput fromI the multivibrator, tube* '15 is of" substantiallx`7v constant frequency and# is, Atherefore, .suitable f'or` control purposes in"'lljeveloping an alternating current suchv as maybeus'edjin driving a syizichronous motor conf.

ceivin'g'ffapparatus to 'be'.s'ynchronized. Y 't o V'lhecircuit-constants ofthe multivibrator/tube nectedL toja' telegraph 'distributor or othelxref 15 are so' adfiustedthat the tubev Will deliver oneiparticularsoutputifrequency under synchro'- nizingcontrolfof eitherlon'e or the other o'f the tone signallingy frequencies.

15 is one sub-har; momie-.of thegmarkingefrequency and another sub-harmonie of the spacing frequency. Thus on onefside the control pulsesY are derived from changesV the conductive .statevv Ithroughj'the; spa'eespathLa inftube'v-IIS, these-pulses Abeing 'trans'- ferired throughfa time constant'circuit which includes-:capacitor f I595 and? -a portion of the p c-i tentiometerll; 1"th-us#-inluencn'g the'janod'e volt` age-:appliedftof'thef-anodefll-in `the fspace" VpatireA .csstori'linterconnectsthacontrolrgrido.; 'm offtubei'l'.

Inthe case of applying controlpulsesfor the.

tripping action in space path d oftube 15 a relatively longer time constant value is assigned to the elements 51, 62 and 63. connected between the anode I and the cathode'l of the tubes ,45 and 15 respectively. This value is such that the marking pulses will produce cathode bias potentials of one value and the spacing pulses will produce cathode biasing pulses of a different value. These pulses are, therefore, varied in amplitude so as to produce a different factor of division in one case than in theother. Since, however, the tripping action is to be maintained constant, the two ratios of division will be made to result in the same output frequency from the tube 15. Y

. More generally stated, the multivibrator tube 15 and its related circuits constitute a frequency changer which accepts marking tone frequency fm and divides it by an integer m; or it accepts the spacing tone frequency fs and divides it by a different integer s. The relation between ,fm and m, also the relation between f5 and s, is such that Therefore, the output frequency obtained from tube 15 is independent of the tone frequency being received.

Capacitor 64 couples the output from tube 15 to the input side of a frequency divided unit 65. Any suitable frequency may b e delivered as output from this unit. Such a frequency may, for example, be 60 cycles. A wave Shaper 66 delivers sinewavef output, say of 60-cycle frequency to an amplifier 61. The outputfrom this amplier unit is then connected to a synchronous motor 68 whose shaft is coupled mechanically to the rotor of the receiving distributor '44. i brushes 39 are mounted for commutation pur-A poses.

In place of the electronic circuit arrangement shown in Fig. 2, Vparticularly that part which comprises tubes 45 and 15, I may, of course, resort to other means for translating the two-k tone'signals into an alternating current of substantially constant frequency suitable for driving the motor 68. For example, if frequency divider circuits are used whose counts are normally independent of theV inputfrequency, then a controlling voltage may be obtained from the locking circuit (tubes 32 and 33), or from Athe subsequent stage 38, and this voltage may be applied to the frequency changer to produce one factor of division during a marking signal and another factor of division during a spacing signal. Fre quency divided circuitsV are well known in the art which are ,capable of dividing, the input frequency by different factors depending upon the application of a varied D.C. bias potential to a suitable tube electrode. If a magnetic relay is used in place of the relay tube 38 a pair ofcontacts may be operated by this relay for applying the control voltage to the frequency divider.

It will now be apparent that the frequency source I at the transmitting station need not necessarily be either highly accurate or extremely stable in frequency. This follows from the fact that both the transmitting and'receiving distributors are controlled in speed from i the v same source l. This desirable operation isobtained without the usual types of phase correction equipment wherein a variable D.-C. controlling volt-y age is utilized. In such equipment the .polarity On this rotorV and magnitude of the controlling voltage depends upon the sense and magnitude of the frequency difference between thetransmitter and the receiver. But the methods of comparing the cyclic rates of thedistributors at the transmitter and receiver respectively have in the past been inaccurate and rather undependable, due to the distortion of code signals as transmitted through the ether path between stations. Such diiculties are avoided by the practice of my invention.

I claim:

1. The method of synchronizing a signal receiver with respect to a transmitter, which comprises generating an alternating potential from which two distinct tone frequencies may be derived by frequency division, so characterizing the marking and spacing elements of the signals that they are represented by one and the other of said tone frequencies respectively, deriving from said alternating potential by frequency division a third or synchronizing frequency capable of use at the transmitter for the purpose of channel time sepa.-V ration of the signals, and deriving from said marking and spacing tone frequencies as received the same synchronizing frequency as aforesaid,

but capable of use at the receiver for the purpose of cyclic distribution of the signal elements into different translating channels.

2. In a telegraph system having a transmitter equipped to send code signals at a constant rate of code elements per second, and having a receiver including a code element distributor for allocating successive code elements to diierent translating units, a single frequency source at the transmitter, means for deriving from said source two modulation frequencies useful for characterizing the mark and space elements of the code signals, a frequency dividerhaving its inputcircuit coupled to said source and having utilization means coupled to its output -circuit for driving the transmitter distributor, means at the receiver for producing modulation frequency responses to incoming code signals, a local alternating current source for driving said receiving distributor and means for maintaining constant the frequency ratios between said local source and each of said modulation frequencies.

.3. A transmitting station including an alternating current generator, means for obtaining from the output of said generator a plurality of sub-harmonic frequency derivatives, a relay operable to-transmit one of said derivatives as a mark signal and a second of said derivatives as a space signal, a distributor for so controlling said Y relay as to provide channel time separation of said Ymark and space signals, and means coupled to and controlled by said -alternating current generatorfor driving said distributor at a speed which bears a constant ratio to the frequency of said generator and which speed bears a predetermined frequency relation to the sub-harmonic frequency derivatives constituting said mark and space signals.

4. A transmitting station according to claim 3 and including in the rst said means a frequency divider unit, a wave Shaper unit and filters individually adapted to pass one and the other of said subfharmonic frequency derivatives.

5. A receiving station including means for discriminating between one and a second of two characteristic frequencies used as tone modulations in the transmission of code signals, a locking circuit operable in response to transitions from one to another of said frequencies, circuit means under control of said locking circuit and including contacts of a receiving distributor for allocating the marking and spacing code elements cyclically to different translating units, and means subject to control by derivatives from both of said tone modulations for producing an alternating current of fixed frequency which bears different xed ratios to the respective modulation frequencies for driving said distributor in synchronous relation to the code element signalling speed.

6. A receiving station according to claim 5 and including in said discriminating means a twin diode discharge tube one space path in which is arranged to rectify a signal component of one modulation frequency and the other space path in which is arranged to rectify a signal component of the other modulation frequency, and connections between said discharge tube and said locking circuit such that flip-op control of the latter is obtained in response to transitions between the rectification of one modulation frequency and the other.

7. A receiving station according to claim 5 and including a multivibrator circuit for obtaining said alternating current of fixed frequency, said multivibrator having input circuits including time constant components operable to produce frequency division by one factor in the presence of one of said tone modulation frequencies, and by a different factor in the presence of the other modulation frequency.

8. In a transmitting station equipped to send code signals at a constant rate of code elements per second, a single frequency source, means for deriving from said source distinct modulation frequencies useful for characterizing the elements of said code signals, a switching device coupled to said means for receiving said modulation frequencies and arranged to deliver any one of said frequencies to its output circuit, a distributor linked to said switching device for actuating the same in accordance with the arrangement of the elements of a code character under consideration, and a frequency divider having its input circuit coupled to said source and having utilization means connected to its output circuit for driving said distributor.

EUGENE R. SHENK.

REFERENCES CITED UNITED STATES PATENTS Name Date Kahn et al Oct. 3, 1944 Number 

